Photocatalysis-membrane separation coupling technology has been a heavily researched area in water and wastewater treatment during recent years. The membrane separation process allows the photocatalyst to be easily separated, recovered and reused. More significantly, the membrane is efficient to maintain high flux of membranes as the photocatalyst can reduce the membrane fouling problem which is a hindrance in the development of membrane process. Moreover, some synergistic effects can also be produced, and thus the efficiency of water treatment is enhanced greatly. A comprehensive review of photocatalysis-membrane separation coupling technology is conducted with an insight into its configurations, theories involved, characteristics, and factors that influence the coupling technology. In view of the existing problems, the prospects for future development are also proposed.
photocatalysis, membrane separation, titanium dioxide, membrane fouling, photocatalytic membrane reactor
Citation:Xiao Y T, Xu S S, Li Z H, et al. Progress of applied research on TiO 2 photocatalysis-membrane separation coupling technology in water and wastewater treatments.Photocatalytic oxidation, a new type of water pollution control technology, with the characteristics of high efficiency, low energy consumption and a wide range of application, can oxidize most organic compounds, especially non-biodegradable organic contaminants, by mineralizing them to small inorganic molecules. For this reason, photocatalytic oxidation technology has broad prospects for application. Among various semiconductor photocatalysts, there is a general consensus among researchers that TiO 2 is more superior because of its high activity, large stability to light illumination, and low price [1−4]. In photocatalytic degradation, two modes of TiO 2 application are adopted: (1) TiO 2 immobilized on support materials, and (2) TiO 2 suspended in aqueous medium [5,6]. Application of TiO 2 in suspension instead of immobilizing the TiO 2 on solid carriers has shown an improvement in organic degradation efficiencies due to the uniform distribution and large specific surface area. However, classical solid-liquid separation processes such as sedimentation, centrifugation and coagulation used for separation of the fine TiO 2 particles (typically less than 1 μm), are not effective [7]. In addition to the low reutiliztion rate, there is also a chance of secondary pollution caused by fine TiO 2 particles in the effluent [8]. Therefore, the recovery of the photocatalysts is one of the main concerns that affect its engineering application on a large scale. A lot of investigations have been conducted aiming at solving this problem. For example, the application of titaniacoated magnetic particles could keep the high photocatalytic efficiency of the suspension system, as well as separate and recover TiO 2 particles from the treated water by applying an external magnetic field [9−11]. Nevertheless, during the integration of TiO 2 and magnetic carrier, the photoactivity of TiO 2 may decre...